In many stairway structures it is desirable to provide for replaceable stair treads and for supporting the stair treads securely. Proper support of glass stair treads, for example, has been a somewhat vexatious problem in the art of stair tread support systems. The support system should, of course, avoid concentration of support forces on the stair tread, securely retain the stair tread in its working position, preferably offer some cushioning for reacting forces exerted on the stair tread when being traversed by pedestrians, and minimize noise transmission or amplification from the stair tread to the stairway structure. It is to meet the desiderata and needs of stair tread support systems that the present invention has been developed.